The present invention relates to puffed food products made from cereal grains in the shape of a small cake or cracker, and the method and apparatus for their manufacture.
Cereal puffing methods are well established in the prior art. For example, gun puffing has long been used to produce discrete, highly expanded cereal products such as puffed wheat or puffed rice. In a typical gun puffing operation, a raw whole grain is placed into a relatively large chamber and a hinged lid is secured. The chamber is then pressurized with steam. After a time, when the chamber has reached a desired pressure and temperature, a lid release mechanism is activated which allows the lid to open suddenly. In the resulting explosion of steam and grain from the chamber, individual grain particles become plastic and undergo rapid expansion until they are many times larger than they were when first placed into the chamber. During the time when the cereal grains are expanding, they are inherently cohesive and adhesive but they do not bond together because the grain particles have little opportunity to contact each other. They are propelled separately from the puffing chamber while they are in the cohesive/adhesive condition and therefore have no opportunity to become bonded together.
Similarly, puffing methods which do not add moisture to the grains during the puffing process but which instead rely only on the moisture in the cereal grains are also well known in the art. An example of such a method is the expansion of cereal grains (especially rice) in an enclosed chamber to produce a puffed food product in the shape of a small cake or cracker.
The apparatus capable of forming such rice cakes is well known. For example, in the 1973 patent to Omer Gevaert (Belgian Patent No. 799,316) an apparatus is disclosed in which a measure of cereal grains is mechanically fed onto a heated piston. The piston and cereal grains are then advanced by a hydraulic cylinder into a heated female mold to create a small, hermetically sealed chamber enclosing the cereal grains. Heat and superatmospheric pressure are thereby applied to the cereal grains until, at a predetermined time, the pressure in the chamber is suddenly released by retracting the hydraulic cylinder. The suddenly depressurized chamber is not, however, sufficiently opened to release the cereal grains by the retracting of the cylinder, but is instead retained in a substantially closed but vented position by a locking device. Therefore, as the pressure is released, the cereal grains expand to substantially fill the chamber and while still in the plastic state bond together to form a small cake or cracker. The locking device is then released, the piston is fully retracted to open the chamber, and the cake is mechanically ejected. Similar devices are disclosed in U.S. Pat. Nos. 4,281,593 issued to Gevaert, 4,328,741 issued to Yoshikazu and 4,667,588 issued to Hayashi.
These cake-forming devices are most frequently used with rice as the cereal grain since rice is capable of relatively easy expansion into a self-supporting cake. The rice used in the process is typically pretreated by washing and tempering steps. For example, in U.S. Pat. No. 4,328,741, the rice at a moisture content of about 15% to 16% is first cleaned by a rice washing machine and received in a basket to be left for 15 to 20 minutes to remove water. The moisture content of the rice immediately after washing is about 30%. Following the addition of salt to the rice, it is dried for a day and then is further dried in a drying machine for two or three hours to a moisture content in the range of 15% to 20%. The rice thus prepared is then ready to be loaded into the rice cake apparatus.
Even though rice pretreated by moisture adjustment and tempering as employed in the prior art expands to form cohesive rice cakes when expanded in a rice cake machine, other cereal grains, when essentially the same pretreatment is applied, expand less readily and form cakes which are both more dense and more fragile than rice cakes. Another problem with the pretreatment of rice by moisture adjustment and tempering as practiced in the prior art is the time required to temper the rice. Yet another problem with prior art rice cakes is their relative fragility and susceptibility to breakage during packaging and shipment.
It is therefore an object of the present invention to provide a grain cake from such cereal grains as wheat, rye, corn, oats, millet, sorghum, barley and buckwheat in which the cereal grains are more highly expanded than those in the prior art.
It is also an object of the present invention to provide a grain cake from such cereal grains as wheat, rye, corn, oats, millet, sorghum, barley and buckwheat which is less fragile than those in the prior art.
It is also an object of the present invention to provide a method for making grain cakes from such cereal grains as wheat, rye, corn, oats, millet, sorghum, barley and buckwheat which employs the same puffing apparatus now used to make rice cakes.
It is also an object of the present invention to provide a grain cake from rice which is less fragile than those in the prior art and less susceptible to breakage during packaging and shipment.
It is also an object of the present invention to provide a method for making grain cakes from rice, wheat, rye, corn, oats, millet, sorghum, barley and buckwheat in which the time required for their pretreatment is reduced.
It is also an object of the present invention to provide an apparatus for pretreatment of such cereal grains as rice wheat, rye, corn, oats, millet, sorghum, barley and buckwheat for the manufacture of grain cakes.